** To make homemade buttermilk, place 1 tablespoon of vinegar or lemon juice in a liquid measuring cup. Fill cup with milk until it reaches the 1-cup line. Let stand for five minutes. Use only ½ cup of the prepared mixture for the recipe.

Steps

Preheat the oven to 350ºF. Cream butter with lemon zest and ⅞ cup of the sugar until light and fluffy.

Add the egg and vanilla and beat until combined. Meanwhile, toss the blueberries with ¼ cup of flour, then whisk together the remaining flour, baking powder and salt.

Add the flour mixture to the batter a little at a time, alternating with the buttermilk. Fold in the blueberries.

Grease a 9-inch square baking pan (or something similar) with butter or coat with non-stick spray. Spread batter into pan. Sprinkle batter with remaining tablespoon of sugar. Bake for 35 to 45 minutes. Check with a toothpick for doneness. If necessary, return pan to oven for a couple of more minutes. (Note: Baking for as long as 10 minutes more might be necessary.) Let cool at least 15 minutes before serving.